Lesson 95: Using a L293D 4 DC Motor Shield | Arduino Step-by-Step Course

Lesson 95: Using a L293D 4 DC Motor Shield | Arduino Step-by-Step Course

In this tutorial, we will explore how to control four DC motors using the L293D motor shield with Arduino. This setup is particularly useful for robotics applications, such as building a robot car, where precise motor control is essential. By the end of this lesson, you will have a working model that can operate multiple motors simultaneously.

The L293D motor shield simplifies the wiring process and allows you to control the motors with just a few connections. You will learn how to wire the shield to the Arduino, set up the code, and execute motor control commands effectively. For a more visual explanation, you can refer to the video at specific timestamps for wiring and coding details (in video at mm:ss).

Hardware Explained

The primary component of this project is the L293D motor shield, which is a quadruple half H-bridge motor driver. This means that it can control two motors in both directions, allowing for full control over motor rotation. The shield connects directly to the Arduino, making it easy to manage power and control signals without messy wiring.

Each L293D chip can handle up to 600 mA of current per channel and operates at voltages ranging from 4.5V to 36V. This range makes it suitable for a variety of DC motors. Additionally, the shield features a jumper that allows you to power both the motors and the Arduino from a single external power source.

Datasheet Details

Manufacturer	Texas Instruments
Part number	L293D
Logic/IO voltage	5 V
Supply voltage	4.5 – 36 V
Output current (per channel)	600 mA
Peak current (per channel)	1.2 A
PWM frequency guidance	1 kHz – 20 kHz
Input logic thresholds	2 V min (high), 0.8 V max (low)
Voltage drop / R_DS(on) / saturation	1.5 V max
Thermal limits	150 °C
Package	16-DIP
Notes / variants	Dual H-Bridge configuration

Ensure motors do not exceed 600 mA to prevent damage.
Use adequate heat sinking for high current applications.
Connect external power before powering the Arduino.
Check jumper placement for powering the shield and Arduino.
Test motor direction by swapping connections if necessary.

Wiring Instructions

Start by connecting the L293D motor shield to your Arduino Uno or Mega. Align the shield's pins with the Arduino's headers and press down firmly. Next, connect your DC motors to the terminals labeled M1, M2, M3, and M4 on the shield. Each motor will require two terminals, so make sure to connect them properly for correct rotation direction.

For power, connect an external battery or power supply to the shield's power input terminals, ensuring the voltage is within the 4.5V to 36V range. Don't forget to connect the jumper on the shield to allow the power to flow to the Arduino. Finally, connect the ground of the power supply to the ground pin of the Arduino to complete the circuit.

Install required library

click on Library icon and search for : Adafruit Motor Sheild Library and click on Install to install it.

Code Examples & Walkthrough

AF_DCMotor motor1(1);
AF_DCMotor motor2(2);
AF_DCMotor motor3(3);
AF_DCMotor motor4(4);

In the code, we initialize four motor objects: motor1, motor2, motor3, and motor4. Each motor is assigned a channel number corresponding to the motor shield's terminal connections. This allows us to control each motor individually.

void setup() {
  Serial.begin(9600); // set up Serial library at 9600 bps
  Serial.println("Robojax L293D Example");
}

The setup() function initializes the serial communication, allowing us to send and receive messages from the Arduino IDE. This is useful for debugging and monitoring the motor control process.

motor1.setSpeed(speed(50)); //set speed for motor 1 at 50%
motor1.run(FORWARD); //send motor 1 to Forward rotation

To control the motors, we set the speed using the setSpeed() method, which takes a value between 0 and 255. The run() method then starts the motor in the specified direction, such as FORWARD or BACKWARD. The speed can be adjusted dynamically as needed.

Demonstration / What to Expect

Once everything is wired and the code is uploaded, you should see the motors rotate according to the commands in the code. Initially, one motor will turn on, followed by the others in sequence, each running for a set duration. If the motors do not operate as expected, check your wiring, ensure the jumper is connected, and verify the power supply is adequate (in video at mm:ss).